The findings come from PTC’s recent “Secret Shopper Campaign” where children between age 12 and 16 visited more than 100 stores in 14 states. During the campaign, 21 stores sold M-rated games to minors.

GameStop, ToysRUs and Shopko sold no such games to minors, with the worst retailers being Sears, K-Mart and Wal-Mart.

The United States Supreme Court has taken up the issue of violent video games this year.